Dual piston engine



Sept. 4, 1934. G. R. SMITH DUAL PISTON ENGINE Filed June 14, 1932 5 Sheets-Sheet INVE TOR.

BY Y

W ATTORIMM/ Sept. 4, 1934. R, SMITH 1,972,497

DUAL PI STON ENGINE Filed June 14, 1952 5 Sheets-Sheet 2 1? lg. g. I I

.D c 23 r A TTORN Sept. 4, 1934. G, SMITH 1,972,497

DUAL PISTON ENGINE Filed June 14, 1932 3 Sheets-Sheet 5 69 VgNTORI M Q Arron/5%.

Patented Sept.

PATENT GFFICE DUAL PISTON ENGINE Glenn R. Smith, Brockway, cane, assignor of onehalf to George Seymour, Brockway, Calif.

Application June 14, 1932, Serial No. 617,074

- 4 Claims.

This invention relates to internal combustion.

engines employing a plurality of cylinders and pistons in which the pistons are connected-to a common crank, and especially to an engine in 5 which the cylinders and pistons are concentrically arranged.

Dual piston engin type connected with esof the internal combustion a common crank are not new.

For instance, stepped cylinders and pistons arranged end for end or in alignment have been made but have not excessive inertia fo proven practical due to the rces encountered because of the weight of the combined or connected pistons and the heavier co nnecting rods, and also due to the fact that engines so constructed are materially increased in over-all height.

The object of the present invention is to generally improve and simplify the construction and operation of internal combustion engines of the character described to provide a multi-cylinder engine in which the cylinders are arranged'in a common plane and concentrically positioned with relation to each other; to provide a piston for each cylinder, said cally positioned and pistons being also concentridisposed on acommon plane;

and further, to provide a connecting rod structure whereby the several pistons maybe connected to a common crank.

The engine is shown by way of illustration in the accompanying drawings, in which- Fig. 1 is a central, vertical cross section of the engine.

Fig. 2 is a similar section but taken at right angles to Fig. 1.

Fig. 3 is aplan View of the upper end of a guide sleeve placed within one of the cylinders.

Fig. 4 is a bottom view of said'guide sleeve.

Fig. 5 is a plan view of the upper end of the cylinders showing the cylinder head removed.

Referring to the drawings in detail, and particularly upper end of which cylinder sleeve B.

Fig. l, A indicates a main cylinder in the is supported a water jacketed This sleeve divides the main cylinder into two chambers, an inner chamber C and an annular concentric exterior chamber D. The cylindersare closed at their upper ends in the usual manner by a common head E. Inlet and exhaust valves of the overhead type, indicated at 2 and 3, (see Fig. 5)

are carried by the head, and

head cylinder,.the inlet ,p

and in the L-head extension of the main orts being indicatedat 4 and 4a and said ports being connected by a dual intake manifold?) and this being, in turn, connected with a carburetors of suitable construction.

The main cylinder A is supported in any suitable manner by a crank case 7 and in this is journaled a crank shaft 8. The structure shown in the present instance is a'two-cylinder motor and the crank shaft employed requires only one crank, such asindicated at 9. Each cylinder is provided with a piston. central cylinder C with a piston 10 and the annular exterior cylinder D is' provided with a piston 11. Wrist pin bosses are formed at the lower end of the piston 11, as shown at 12, and these carry a wrist pin 13, the piston 10 being connected with said wrist pin through a rod 14 and the wrist pin being otherwise connected with the crank 9 through means of a main connecting rod 15. A standard form of cam shaft is employed, as shown at 16, and it is driven at a two to oneratio as the engine illustrated is of the four-cycle type. The cam shaft differs from ordinary cam shafts only to the extent that it is provided with four cams, two inlet cams and two exhaust cams, as there are two inlet valves and two exhaust valves. The valves 2a and 3a are directly actuated from the cam shaft while the valves 2 and 3 in the head E are actuated by pusher rods and rocker arms, as shown. The piston 10 may be exceedingly short and consequently light in weight due to the fact that the connecting rod la is not subjected to rocker movement and rod 14 may also be light in weight for the same reason and for the additional reason that the loads imposed thereon are only compression and tension loads. The piston 11, on the other hand, must be comparatively long as it carries the wrist pin bosses and these must clear the lower end of the cylinder sleeve B. This piston may, nevertheless, be comparatively light in weight as its form is nothing more nor less than an elongated sleeve, this being possible as said sleeve, or in other words, skirt portion is guided both on its inner and exterior surfaces; the exterior of the cylinder sleeve B guiding the interior surface of the piston sleeve or skirt 11 and a guide sleeve 17 engaging and guiding theexterior surface'of the skirt.

The guide sleeve 17 disposed at the lower-end oi thecylinder A is here shown as a separable or insert member. The upper end of this sleeve is provided with cut out portions 18, asshown in Fig. 3, while the lower end has openings 19 formed therein, as shown in Fig. 4; the cut out portions or openings forming ports which relieve suction and compression on the lower side of the piston 11 during reciprocal movement thereof.

In actual operation each piston will be provided with ring grooves and rings, as illustrated. In addition thereto a set of ring grooves and rings will be provided at the lower end of the cylinder sleeve B, as indicated at 21, these being essential to prevent leakage around the inner surfaces of the piston 11 while the upper end will take care of leakage around the exterior surface. The rings in the piston 10 will obviously function in the usual manner.

The engine illustrated operates on the fourcycle principle, that is, thecycles are as follows: Suction, compression, firing and exhaust. The cycles alternate in the respective cylinders and there will accordingly beone firing stroke for each revolution of the crank shaft, this being an important feature as it produces a very material improvement in the turning torque of the crank shaft when comparison is made with a single cylinder engine of the samehorsepower. The engine may be water cooled as here illustrated, water being ci culated through the jackets and the head in any suitable manner. Clearance for the inlet and exhaust valves carried by the head E 5, baffies or like devices being placed in the head to crank shaft.

insure proper circulation downwardly through one set :of openings and upwardly through the other supply will obviously be provided, but as a standard form of ignition system may be employed no illustration thereof has been made. Suflice it to say, that one spark plug will communicate with the inner cylinder C and a second spark plug with the exterior or annular cylinder D, and that the plugs will fire alternately so as to produce one firing stroke for each revolution of the Such a firing arrangement is desirable for two reasons: First, as previously stated, to obtain a more uniform turning torque; and secondly, to counteract the inertia forces produced by the reciprocating parts such as the pistons, connecting rods, etc.; that is, when piston 10 is driven downwardly during the firing stroke piston 11 in on its suction stroke. When piston 10 is exhausting piston 11 is compressing; when piston 10 is on its suction stroke piston 11 is firing, and when piston 10 is compressing piston 11 is exhausting. Hence, during each outward or upward stroke of the pistons, one piston will be compressing and during each downdward stroke one piston will be under suction. Inertia forces produced by the reciprocating parts are thus more or less offset by either compression or suction and vibration due to inertia forces is materially reduced. Furthermore, inertia forces in an engine designed as here shown should be comparatively small as the total piston weight of the combined pistons should not exceed the weight of an ordinary piston designed for the same amount of horsepower. Cylinder wear in the cylinder C due to piston slap is entirely absent in this structure and wear in the annular cylinder D should be reduced to an absolute minimum due to the double guiding faces provided for the skirt of the piston 11.

The essential features of the present structure are: First, the arrangement of two cylinders in a common plane and one cylinder concentric to the other; Secondly, employing pistons also arranged in a common plane and concentric with relation to each other; Third, subjecting said pistons to an alternating firing period so that one explosion is'obtained for each revolution; Fourth, employing pistons of a substantially different area and stroke; Fifth, providing ample guiding surfaces for the pistons; and Sixth, providing a connecting rod structure whereby both pistons can be operated in unison and by a common crank.

These are the essential features and are subject to changes in detail when construction and design is considered. The arrangement of the valves, the cooling jackets, the spark plugs, the manifolds, etc., may obviously be changed to suit 1 varying conditions and while other features are more or less specifically described, I wish it understood that various changes may be. resorted to within the scope of the appended claims. Similarly, that the materials and finish of the several 105 parts employed may be such as the manufacturer may decide, or varying conditions or uses may demand. I

Having thus described my invention, what I claim and desire to secure by Letters Patent is- 1. In an engine structure of the character described, a pair of cylinders concentrically arranged one within the other, a piston in the inner cylinder, a piston in the outer cylinder, a wrist pin carried by the last-named piston, a connect- 115 ing rod connecting said wrist pin with said piston in the inner cylinder, and a second connecting rod connecting the wrist pin with a common crank.

2. In an engine structure of the character described, a main outer cylinder, 2. water jacketed 120 sleeve within said cylinder and spaced therefrom to divide the cylinder into an inner cylinder chamber and an outer annular cylinder chamber, a piston in each cylinder chamber, a wrist pin carried by the piston in the outer cylinder chamber, a rigid connecting rod connecting said wrist pin with the piston in the inner cylinder, a second connecting rod connecting the wrist pin with a common crank, a sleeve-like extension on the piston in the outer cylinder, and means exteriorly and interiorly of said sleeve for guiding the same.

3. In an engine structure of the character described, a main outer cylinder, a water jacketed sleeve within said cylinder and spaced therefrom to divide the cylinder into an inner cylinder chamber and an outer annular cylinder chamber, a piston in each cylinder chamber, a wrist pin carried by the piston in the outer cylinder chamber, a rigid connecting rod connecting said wrist 140 pin with the piston in the inner cylinder, a second connecting rod connecting the wrist pin with a common crank, and a guide sleeve in the lower end of the main cylinder, said sleeve forming a guide for the exterior surface of the skirt of the piston in the outer cylinder and said water jacketed sleeve forming a guide for the inner surface of said skirt.

4. In an engine structure of the character described, a main outer cylinder, a water jacketed 0 of the main cylinder, said sleeve forming a guide for the exterior surface of the skirt of the piston in the outer cylinder and said water jacketed sleeve forming a guide for the inner surface of said skirt, and ports formed in the guide sleeve to relieve the lower end of the piston in the outer cylinder chamber from suction or compression resistance.

GLENN R. SMITH. 

